package J7_8;

import java.util.Scanner;

public class demo {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        double n = in.nextInt();
        double m = in.nextInt();
        double res = combination(m, n);
        for (int i = 0; i < m; i++) {
            res *= 0.8;
        }
        for (int i = 0; i < n - m; i++) {
            res *= 0.2;
        }
        String formattedNumber = String.format("%.4f", res);
        System.out.print(formattedNumber);

    }
    public static long factorial(double n) {
        if (n == 0 || n == 1) {
            return 1;
        } else {
            long result = 1;
            for (int i = 2; i <= n; i++) {
                result *= i;
            }
            return result;
        }
    }
    public static long combination(double n, double m) {
        if (m > n) {
            return 0;
        }
        return factorial(n) / (factorial(m) * factorial(n - m));
    }
}
